John e



J. E. HILBISH.

TWO-WAY TRUNK CIRCUIT. APPLICATION F|LED1uLy1s.|91s.

1 ,3 1 6,892. Patented Sept. 23, 1919.

75L/527725K' @MM La/522522715295.

y UNITED STATES PATENT OFFICE. l

' .'ioHN E.' HILBIsH, or LA GRANGE, ILLINOIS. AssIGNoR rro KELLOGGsWITcHBoARD AND lSUPPLY COMPANY, OF CHICAGO, ILLINOIS, ACORP0IRA'J'.IO1\T OF ILLINOIS.

TWO-WAY TRUNK-CIRCUIT.

Specification of Letters Patent. Patented Sept. 23, 1919.4

Application led July 16, 1915. Serial No. 40,81.

To all whom t may concern.'

Be it known that I, JOHN E. HiLrsi-r, a citizen of the United States ofAmerica, residing in La Gran e, county of Cook, and State of Illinois,ave invented certain new and useful Improvements in Two-VayTrunk-Circuits, of which the following is a specification.

`My invention relates to telephone systems and has more particularly todo with systems using link circuits and-trunk circuits for use incompleting connection between subscribers in the same exchange andbetween subscribers in different exchanges and has for its object, anovel and improved system of the above type.

One of the features of my invention is the provision of an improved cordcircuit in which the moment a ringing key plunger' is depressed, ringingcurrent is automatically connected to the circuit connected with thecalling end of the link circuit, no matter in what `position theinterrupter mechanism may be in, which mechanism thereafterl operates tointermittently apply ringing current to the said circuit. The feature ofproviding the above-described so-called preliminary ring insures theproper operation of the .trunk circuit apparatus when the cord circuitis used for extending a call to a distant exchange through the medium ofa trunk circuit.

I Another feature of my invention is the provision of animproved two-waytrunk circuit for use between common battery exchanges and local batteryexchanges, which is most simple but yet positive in its operation. Otherobjects of my invention will be pointed out in the appended claims.

For a more complete understanding of my invention reference may be hadto the accompanying drawing in which only suflicient apparatus is shownfor connecting the calling subscribers line at one exchange with acalledl subscribers line at a second exchange. The connection iscompleted through the medium of the calling `subscribers line circuit L,link circuit C at the first exchange, trunk circuit D extending to thesecond exchange,- link circuit E at the second exchange and calledsubscribers line circuit L1 at the said seond exchange.

Referring now more in detail to the apparatus illustrated, thesubstation A may be of any well-known or suitable common batteryv type.The line circuit L comprises the line relay LR, cut-ofi' relay CO,multiple jack J and multiple line lamps S. The line circuit illustratedis known as a multiple line lamp circuit in which a line lamp isprovided for each line jack so that when a call is initiated a lightedlamp appears before each of the multiple line `jacks so that any one ofa plurality of operators may seize the calling line to the exclusion ofthe others.

The cord circuit C comprises an answering plug AP and a calling plug CPconnected by the `heavily marked talking conductors. Upon the initiationof a call, the operator answers by inserting the answering plug AP .intoa multiple line jack J, causing the energizatioii of the test relay TEwhich connects an answering sleeve supervisory relay AS in seriescircuit with the cut-off relay CO of the line circuit L, the relay ASopeating to connect the operators set O to the cord circuit. Theanswering tip supervisory relay AT is also energized to preventanswering supervisory lamp AL from glowing prematurely. The operatorupon learning the wants of the calling subscriber will plug directlyinto the jack of the called subscribers line, if the called subscriber-sline terminates in the same exchange, or will plug into the jack J1connected to the trunk circuit D, which ex-` tends to` a secondexchange, if the called subscribcrs line terminates in the secondexchange. Upon the insertion of the calling plug CP into either of saidjacks, the calling supervisory relay CS is energized to disconnect theoperators set O from the cord circuit. One of the ringing key plungersof the ringing key RK is then depressed, which connects one of aplurality of generators to the connected line. The common contacts 2 and3 of the ringing key are also operatedv when the plunger is in its fullydepressed position to close an energizing circuit for ringing disconnectrelay RD which in turn closes an energizing circuit for an interrupterrelay IR, which is alternately, energized and de'energized tointermittently connect ringing current to the connected line. At thesame time that thejringing disconnect relay RD is energized, apreliminary energizing circuit is closed through the interrupter relayIR, thereby connecting ringing current to the connected line theAinstant that the end contacts 2'and 3 are operated. .This preliminarycircuitis held closed only during the fully depressed position of theringing key. A meter relay MR and meter mag-V net MM are provided andoperated when the common contacts are *closedvto operate the metertoregister. Y. 'A calling, tip supervisory relay CT is also provided,which is energized upon the removal` of the receiver at the calledsubstationl if connection be directto' a called substationor upon thebridgingV of the impedance't across the trunk conductors 5 and 6 if theconnection isextended to a second exchange, to disconnect ringingcurrent from the connected line and to efface `the-calling supervisorylamp CL.A l

replace his Should the calling subscriber receiver before the calledsubscriber answers, the link disconnect relayLD is energizedwhich'c-auses the denergization of the relays RD and IR to interrupt theringing current, which is being intermittently connectedto the line'through the medium of thev interrupter I.V The energization of the linkdisconnect relay LD also causes the disconnection of the link conductorsfrom the calling line, which causes the restoration of the sie'connected calling line circuit topermit the calling subscriber toimmediately recall without awaiting the removal of the answering plug APfrom the connected jack J.

" The trunk circuit D is a two-way trunk circuit and is used forextending connectionsl A between a common battery exchange Yand amagneto exchange. It'comprises a control magnet CM which is bridgedacross theV trunkconductors 5 Vand 6 and fwhich responds to ringingvcurrent to close a self-lock-V ing circuit throughthe callA signal lampCSL. The release magnet RM'responds to the insertion of the calling plugCP into jack Y n J 1 land operates 'tof open the circuit vof `the n ,lrstore its armature.`

control magnet 'CM' and to mechanically re- The magnet `7 is bridgedacyrossv the trunk conductors behind'the con` densers K and'K1L whichcon'ductively unite the strands ofthe trunk circuit and responds togenerator current fromV the distant magw netofexchange. The magnet 7,.uponyenergi'zing, closes a circuitl through the relay 8, which in turnenergizes and bridges the impedance 4E across the trunk conductors. Thetrunk circuit D terminates in ajack J 2 and an associated trunk dropTD,-in the mag-` lneto exchange. ."The link circuit E comprisesananswering plug'APl and a calling plug CP1 conductively connected by apair of condensers K2 andfK? and is provided. with an answeringsupervisory rdrop ASD and acalling,supervisoryjdrop CSD. The usualringing and'listening key 9 is provided for connecting the uoperatofsset O1 to the strandsof the cord` circuit or for associating V,thegenerator ,G1 with the strands of the calling "plug CP1.The'"'subscribers substa' stat-ion A initiates a call, theline relayLB',V

is energized closing a circuit for the line signalsS. An operator seizesthe call by insert@ .ing'the answering -plug AP into one of the multiplejacks J of the calling line'. The test relay TE Vis energized to closeits alternate Contact 12 which closes a series energizing circuit`including relay AS and the *cut-0H relay CO. The relayAS isfnowconnected to the sleeve conductors of plug AP independent of thecontact12 of the relay TE by way of its alternate contact le and oper-` ates toconnect the operators set O throughY its alternate contacts 15, 16J` tothe talking strands of the cord circuit. Therelay AT is also energizedupon the insertion of the plug AP into the multiple jack J and operatesto prevent the premature glowing ofthe supervisory lamp AL. The"cut-ofi'l relay CO of the line circuit L. upon energizing,"

` disconnects the line relayLR, whichV efaces the line lamps S'.Y Y'Should av second operatorv attempt to answerthe initiated call,fthe lowwound answering relayAS of the virsteord,

circuit prevents thejhigh resistance relay TE- i of the second'cordcircuit `fromoperating dueto the shunting effect of therelayAS'of thefirst cord circuit, andthe second'operator not being able tocommunicatel witht'he call*` ing subscriber, knows that the initiatedVcall has been seized by anotheroperatorand removes her answering plug APfrom the multiplev .jack J L The connected operator now as certains thewants .of the calling subscriber, andv assuming that. substation YFfiswanted, whichterminates in lineV equipment Y attlie second.exchange,gthe operator Vmakes 1175 the usual preliminarytest, andassuming that trunk circuit D is idl'e,insertsthe call-V ing plug CPinto the trunk jackl J 1. .The in# sertion ofthe calling plug.. CPy intojack J1 closes auseries energizing circuit including VV releasemagnetRMand the calling sleeve su-v Y pervisory relay CS.V RelayRM,`upon energ1zing,.opens the circuit of the controlling magnet CM atits` contacts 17 and18'. The relay QS,.upon energizing, opensits normalcontacts'4 19 and 20 disconnecting theoperfators set() fromthe cordcircuit and closinga circuit for the calling supervisoryY lamp CL,A.traced from'battery through the said lamp, through` normalr contact 22ofV relay 150V RD, normal contact `23 of relay CT, and' throughalternate .contact 21 of said relay CS to ground. The operator novidepresses a ringing plunger of the ringing key RK to connect ringingcurrent to the strands of the trunk circuit D, thereby throwing thetrunk drop in the 4distant exchange. The ringing plunger, upon beingdepressed to its fully operated position also .closes the cornmoncontacts 2 ,and 3, but when the plunger assumes its indicating positionthe said common contacts restore to normal. The closure of alternatecontact 2 closes a circ-uit through meter relay MR traced from battery`through the winding of said relay, alternate contact.

2, normal contact 25 of relay RD, normal contact 26 of relay LD, normal.contact 23 of relay CT, and through alternate contact 21 of relay CS toground. The meter relay MR, upon energizing, closes its .alternatecontact .27 thereby closing a circuit through meter magnet MM to stepthe meter mechanism to register the call. The closure of the commoncontact 3 closes an energizing circuit through the ringing disconnectrelay RD and through .the interrupter relay IR, the latter circuitextending from battery through the lower Winding of said relay IR,alternate contact 3, normal contact 23 of re.` lay CT, and alternatecontact 21 of relay CS to battery, thus causing the relay IR to energizeandconnect ringing current to the trunk conductors 5 and 6 as long asthe ringing plunger isheld depressed. The circuit for the ringingdisconnect relay RD extends from battery through Winding of said relay,alternate contact 3, normal contact 23 of relay CTv and alternatecontact 2]. of relay CS to ground. The ringing disconnect relay, uponenergizing, `closes a locking circuit for itself through its alternatecontact 25 independent of the common contact 3, said circuitextendingfrom battery through said relayl RD, its alternate contact 25, normalcontact 26 'of relay LD, normal contact 23 of relay CT and alternatecontact 21 of relay CS to ground. The ringing disconnect relay RD, uponenergizing, .also disconnects the talking strands of 'the' cord circuit,connecting the plugs AP and CP and closes an ener'- .gizing circuitthrough the interruptor relay IR traced from battery `through theinterrupter I, upper `Winding of said relay IR, normal contact 30 ,ofrelay CT, alternate contact 22 of relay RD, normal contact 23 of relayCT andalternate contact 21 of relay CS to ground. However, this circuitis only operative to energize the interrupter relay IR when connectionis extended directly to the jack of the called subscribers line. `Theinterrupter relay, upon its first energization, dueto the directvclosure of valternatecontact 3.,closed `a circuit extending from theselected generator over the common ringing conductor 31,.alternate con-`tact `32 of interrupter relay IR, .tip .conductors of plug CP and jackJ1, and l,condenser K, here the circuit divides, part of the current`passing through magnet 7, therest eX- tending through the `trunk dropTD back over the opposite trunk conductor wherethe circuits .again joinand extend through lthe condenser K1, sleeve conductors of jack AJ1 andplug CP, .alternate contact 33 of relay IR to ground and back to thegenerator. The relay 7, upon energizing, closesanenergizing circuitthrough -the relay M8, Which upon energizing, closes .a locking circuitfor itself through its alternate contact 35 and bridges impedance lacross the trunk `conductors 5 and G through its alternate eontact 36.The bridging of the impedance 4 across the trunk conductors closes anenergizing circuit through the calling tip supervisory relay' CT. Thiscircuit extends from ground through the `upper Winding of relay CT,normal contact 320i relay IR, tip conduetors of plug CP and jack J1,alternate contact 36 of relay 8, impedance 4, ring contacts of jack J1and plug GP, normal contact 33 of relay IR, through the lower winding ofsaid relay CT .to battery. The relay CT upon energizing, opens thecircuit of the ringing disconnect relay RD at its normal contact 23 andopens the circuit of interrupter relay at its normal contact 30. Theclosure of the circuit through trunk drop TD causes the said drop to beoperated to slgnal the operator at the second exchange. It has beenfound essential to close the above traced preliminary circuit throughthe interrupter relay IR, before Waiting for the interrupter circuit tobe closed therethrough, otherwise if the ringing disconnect relay RDshould be energized just as the interrupter I is turning from itsconductive path to its insulated path, the interrupter relayIR will beenergized momentarily and not supply sufficient ringing current tooperate the trunk drop at the distant exchange before the relay v7operates to cause relay 8 to bridge the impedance 4 across the .trunkconductors and cause the calling tip supervisory relay to permanentlyopen the circuit vof the interrupter relay IR.' The preliminary ringingcircuit is also a great help When ringing called subscribers direct asit causes the bell o1 the called subscriber to be signaledthe instantthat the plug is inserted into the jack of the said .called line and theringing plunger depressed. The operator at the distant exchange, notingthat the trunk drop TD is operated, inserts the answering plug AP ofcord circuit E into the jack J 2 opening the circuit of the trunk dropTD at contact 37. She then operates the ringing and listening key 9 toconnect her telephone set O1 acrossthe conductors of the cord circuit Eso that she may inquire the wants of the calling subscriber.4 Uponlearning that the Y subscriber atsubstation F. is desired,she insertscalling plug CP1V intojack J 3, thereby `disconnecting the -line drop*LDl by opening normalcontact 38.A The operator nextoperates the ringingand listening key in the op# posite direction to connect the generatorkGrl across the line of thecalled subscriber.` The calledsubscriber-upon answering may` now carry on conversation withthecallingjsub? denergizing, closes its normal contact 45V thereby closing acircuit through the'an- Y swering supervisory lamp AL and' link dis?connect relay LD.: Thel latter circuit extends from battery through saidrelay. LD, said normal ContactA of relay AT, alternate contact 39" ofrelay AS and alternate Contact 21 of relay CS to ground. The* relay LD,upon energizing, opens the cord circuit conductors at contacts 40 and 41and opens theseries energizing'circuitvfor the-relay CC and AS at itscontact42. However, a substitute cir-cuit is closed ltor the relay ASbefore -it has had timeto denergize, said circuit extending from batterythrough the said'relay, its alternate contact 14, the alternate Contact42' of relay LD, alternate contact 39 ofsaid relay AS `and through thealternatefcontact 21 of relay CS to ground.` Relay CO:denergizingfrestores the line circuit of the calling line to normalplacing it` incondition for an immediate recall so that if thesubscriber at substation A again removes his receiver, the line. relayLR is energized to light themultiple line signals S so that the ysameoperator or another operator may seize avrecall without awaiting theremoval of the plug AP. The operator at the link vcircuit C, noting theglowing of the supervisory lamp AL, removesthecalling Vplug CP 4from thejack J1' and'thereby allows the Vapparatus of the trunk circuit D and ofthe cordcircuit C toy return to normal. I` The operation of thegenerator 10 at the called substation F Aoperates the callingsupervisory'drop-CSDto notify the opera* tork at thetrunk circuit E thatconversation has terminatedi The operator then removes the 'calli'ngplugy CP1 and the answering plug Y 'Y AP1 fromtheirrespectivejacks J3 and J2,

thereby permitting the remainingapparatus Y used in the trunkingconnectionto restore to normal. y Y. l Y Now,assuming that aysubscriberat the magneto exchange, subscriber at substation F desiresla connection .with a subscriber' a1;-

- scriber -F first removes his receiver andthen operates the generatorlOto throw the line drop LD1. The operator, upon noting this signalinsertsthe answering plug APfL o f the link circuit D into jack J 3 'ofthe subscribers line equipment L1.V The operator next Y throws thelistening key V9y to connect herA telephone O1 across the line of the`calling subscriber and inquires his wants. The operator upon learningthat a subscriber at the common battery exchange is desired insertsthe'calling plug CP1 intoxthe jack J 2 connected to the trunk circuitDyand* operates the key 9 to bridge theringing generator G1 across the"trunk xcircuit. The relay. 7 flocated at the-'common batteryexchange'in re#V sponse to this connection of ringing current to thetrunk conductors yoperates to closeia circuit through the relay`8.; Therelay 8 enL ergizes but: its operation isffunctionless'at this time. YAt the same `time that relay 7 is operated the control-magnet CMis alsoopY erated due to the bridged ringingcurrent at' the magneto exchange.The control magnet,

upon operating, closes a circuit through the signal lampCS-L. Theoperator at the common battery exchange,noting theV glowing of the lampCSL, inserts the answering plug Vof a cord circuit-'into the jack J1 andinquires the wants of the calling subscriber.1 This cord circuitmaybeofany suitable or approved type of three-conductor cord circuit.

Upon the insertion yor' thev answering plug into the jack, J1, themagnet RM is energized and operates to restore the armature of themagnet CM, thereby'ei'acing lamp CSLandY removes the winding of the samefrom acrossy conductors 5 and 6 ofthe trunk circuit D. Y

The operator then inserts the calling plug into the jack of the calledlineand signals' the called subscriber .in theusual mannen Alfter the.conversationis inishedvlh Sub Y scriber at substation F operatesgenerator-'10.

to causeV the answering supervisory drop ASD to be operated. VTheoperator at the. magneto exchange -upon noting the position` ofthe dropASD removes the plugs-of the cord circuit E from the Vjackofthe callingline and Vfrom* the jack J Zof the trunk circuit D.` 'The operatorat thecommonl bat- 1 tery exchange upon noting the disconnectv d signal causedby the called subscriberref placing his receiver, removes the' plugs ofthe cordcircuit used in establishing the con-j nectionfandV therebypermits the apparatus a of the trunkcircuit D` and at the-"called sub'fVscribers line circuitto return' to normal'.

VlWhilc I have illustrated theV preferred em?V Y* bodiment of myinvention in certain speciic clrcuit arrangements, yet 1t'1s to beunder-`V stood that I do not wish to be limited tothe'- i same as manychangesand modifications 'willfV readily suggest'- themselves to one4skilled in the art, 'therefore' -I wish tofcfover' ally that which comesWithiny the spirit 'and scope or' the-appended claims.

Having described my invention, What I claim as'neW and desire to secureby United States Letters Patent, is:

1. A telephone system comprising a common battery subscribers line and alocal battery subscribers line, a link circuit and a trunk circuit forconnectin saidv lines, means controlled from said li circuit foroperating a signal at the distant end of said trunk circuit, automaticmeans for disasseciating said operating means, and means individual tosaid link circuit for insuring the operation o f said signal.

2. A telephone system including a calling subscribers line and a calledsubscribers line, a trunk circuit for connecting said lines, a ringingcurrent generator associated With said trunk circuit, a signal deviceassociated With said trunk circuit, automatic means for connectingcurrent from said generator to said trunk circuit, a manually controlleddevice independent of said trunk circuit for initiating an operation ofsaid automatic means, automatic means associated with said trunk circuitfor disconnecting the said ringing current generator from the trunkcircuit, said manually controlled means operating said automaticVringing means in such a manner as to insure the operation of saidsignaling device.

3. A telephone system including a trunk circuit, means bridged acrossone end of said trunk circuit for displaying a signal, signaling meansassociated with the opposite end of said trunk circuit to cause suchdisplay, and a coil bridged across said trunk circuit for disconnectingsaid signaling means, and means to insure the operation of said lirstmeans.

4. A telephone system comprising a common battery line and a localbattery line, a link circuit and a trunk circuit Jfor connecting saidlines, means controlled from the link circuit for operating a signaldevice associated With said trunk circuit, automatic means associatedwith said trunk circuit for automatically discontinuing said firstmeans, and means individual to said link circuit for insuring that saidsignal will be operated before said automatic means operates.

5. A telephone system including common battery and local batterysubscribers telephone lines, a manually controlled link circuit andamanually controlled trunk circuit or interconnecting said lines inconversational circuits, means responsive to the connection of said linkcircuit to said trunk circuit for operating a signal at the distant endof said trunk circuit, automatic means for disassociating said irstmeans, and means individual to said link circuit for insuring theoperation of said signal before said-1 -disassociating meansdisassociates said operating means. Y

6. A telephone system including a link circuit and a trunk circuit, a`visual' signal for said trunk circuit, automatic ringing means for saidlink circuit for operating said' visual signal, trunk circuitmeans fordisconnecting said automatic ringing means froin'said trunk circuit, andkey controlled means individual to said link circuit for operating saidautomatic ringing `means to connect it with said trunk circuit for aperiod of time suiiicientin duration to operate said trunk signal beforesaid trunk means operates to disconnect said automatic ringing means.

7. A telephone system including subscribers telephone lines, linkcircuit and a trunk circuit for connecting tWo of said lines inconversational circuit, a signal device associated With the distant endof said trunk circuit, automatic ringing means for said link circuit foroperating said signal device, means associated with saidI` `trunkcircuit for disconnecting said automatic ringing means, and manual meansindividual to said link circuit for connecting said ringing current tosaid trunk circuit for a period of time sufficient to insure that saidtrunk signal will be operated before said disconnect means operates todisassociate said automatic ringing means.

8. A telephone system including a link circuit, automatic ringing meansfor said link circuit, a called subscribers line, a trunk circuitprovided With a signal, said link circuit adapted to be connected toeither said subscribers line of said trunk circuit, and means forcausing a preliminary operation of said automatic ringing means toeither signal said called subscriber or to operate said signal.

9. A telephone system including subscribers telephone lines, a linkcircuit and a trunk circuit for connecting two of said lines inconversational circuit, a signal device associated With one end of saidtrunk circuit, automatic ringing means for. said link circuit foroperating said signal device, means associated With said trunk circuitfor disconnecting said automatic ringing means, and means individual tosaid link circuit for connecting said ringing current to said trunkcircuit for a period of time sufficient to insure that said trunk signalWill be operated before said disconnect means operates to disassociatesaid automatic ringing means.

10. In a telephone system, the combination of a link circuit connectedto a trunk circuit, a signal for said trunk circuit, signaling means forsaid link circuit for operating said trunk circuit signal, meansassociated with said trunk circuit for disconnecting said signalingmeans from said .trunkg circuit, andmeans individual to said ltiopieskof this vpatent mayibe obtained for link circuit forinsuringlthat said signaling Vmeans Will bevconnected to. saidtrunkcircuit ffor a: periodV of time suficient tooperatersaid trunk circuitsignal. Y i Y f 11..7Invatelephone system, the combinationof aplug-ended link circuitconnected toa jack-ended trunkv circuit,signaling means jassociated With said link circuit, asignalassociatedwith said 'trunk circuit, afmanually controlled ringingkey` for associating said signaling means With c said trunk circuit tooperate saidrtrunk signal, automatic means associatedwith 'the trunkcircuit-fori disconnecting said signaling means, and means individual tosaid' link circuitrfor insuring the operation of said trunk circuitsignal. 129A telephone .system includingja subscribersf line terminatingina three-conductor jack and fa second subscriber-s line terminating ina Ytwo-,conductor jack, a link Vcircuit and a trunk circuitiforconnecting said jacks, signaling'means associated With 1n-lessa saidlinkcircuit, aVv signal associated With said trunk circuit,l means forvassociating said signaling means` Withfsaid signal, automatic means fordisassociating said signaling means, and meansindividual to saidY linkcircuit for insuring thejoperation of Vsaid signal S13. 'A telephonesystem.y includingV sul);-V

scribersl lines of different charactena link circuit and; a trunkcircuitfor connecting*y .of Cook and State of Illinois, ini the presenceofltWo Witnesses; l

l JOHN- isgHiLBrs'Hjk ,Witne'sses'p A 'I v ,Y y

1 l j,P.fH. MAILINCKRODT.

B. Onnilv.-Y

five cents each, addressing-.the Commissioner of Patents, Washington,13.0. l

